Pulsating Ticking Sound from Passenger Side Even When the Motor is Off

[bethacker]

Background:
I recently bought a 99 ranger XLT 4x4 with the 4.0 OHV engine (200k miles). I'm brand new to vehicle maintenance and wanted to use the ranger to learn. I just replaced the water pump, power steering, thermostat, alternator and some other things.

Problem:
I've been driving it for a little over 2 weeks with about 500 miles but recently noticed that there is this ticking/pulsating sound coming from the passenger side of the motor. It happens after I've driven for about 10 minutes, the engine temp hits around 199F and I am idling. If I rev the engine the sound goes away but comes back as soon as it idles. It keeps going even after the motor is off for about a minute or 2. It does not occur when the engine is cold but if I sit there and let the engine come to temp, the sound starts.

I'm thinking it might be an air bubble in the radiator line since it is pulsating but I'm not sure. I've tried bleeding the coolant again, even parking on a hill and bleeding it. I'm 95% I got all the air out.

Here is the video of the sound https://drive.google.com/file/d/1ASgph5ayErNYQVywP4YouUeyz3ANtoZL/view?usp=sharing

 

[bobbywalter]

Pull the vacuum line off the reservoir from check side and see if it stops.